The PREPROCESS global target is available for use in core builds.

When specified, rather than performing a build, Raptor uses the compilers that
would normally be invoked in the build to generate preprocessed versions of
a component's source files.  These files are generated into the source tree
alongside the source files themselves, and have filenames that are
appropriately tagged based on the configurations used.  No further build is
performed.  The general format of the generated filenames is as follows:

    source_filename.build_platform.build_variant.target_name.pre

An example, based on the build of a helloworld.exe component using the default
winscw and armv5 configurations:

    G:\HelloWorld>dir /b
    bld.inf
    HelloWorld.cpp
    HelloWorld.mmp

    G:\HelloWorld>sbs preprocess

    G:\HelloWorld>dir /b
    bld.inf
    HelloWorld.cpp
    HelloWorld.cpp.armv5.udeb.helloworld.exe.pre
    HelloWorld.cpp.armv5.urel.helloworld.exe.pre
    HelloWorld.cpp.winscw.udeb.helloworld.exe.pre
    HelloWorld.cpp.winscw.urel.helloworld.exe.pre
    HelloWorld.mmp

The PREPROCESS target currently works for files listed in .mmp files using
SOURCE and that would, in normal build operation, be compiled for e32 and
emulator configurations; .pre files represent what would be compiled for the
processed configurations in an actual build by the compilers used.

Notes:

*  The PREPROCESS target assumes that source dependencies are satisfied,
   therefore would typically be used "post-normal build" where the build itself
   generates source that is used in compilation.
*  As this is primarily a developer aid, .pre files are not reported as
   releasable output.  However, they are removed in clean operations if the
   PREPROCESS target is used.
*  For configurations where PREPROCESS is not currently supported, it will
   simply do nothing.
*  TARGET name is used in generated filenames in order to support distinct
   preprocessor output for source files that are built from more than one .mmp
   file.
